The present invention relates to the field of phased array systems, and more particularly to a technique for digital formation of multiple independent beams on transmission.
It is well known that phased antenna arrays can be configured to provide the capability of transmitting multiple independent beams. See, e.g., "Introduction to Radar Systems," Merrill I. Skolnick, McGraw-Hill Book Company, second edition, 1980, pages 310-318. The typical techniques for producing multiple independent transmit beams include complex feed networks with multiple phase shifters (one set for each beam), complex lenses or complex hybrid phasing matrices. These techniques can all be shown to have relative weight, size, performance and cost disadvantages, particularly for space and airborne radar application.
Techniques have been described in the literature for generating multiple beams on receive by digital beamforming techniques. "Digital Multiple Beamforming Techniques for Radar," Abraham E. Ruvin and Leonard Weinberg, IEEE EASCON '78 Record, pages 152-163, Sept. 25-27, 1978, IEEE Publication 78 CH 1354-4 AES. No description appears in this reference of forming independent multiple transmit beams by digital beamforming techniques.
It is therefore an object of the present invention to provide a phased antenna array system having the capability of generating multiple independent beams without the use of multiple sets of phase shifters, complex lenses or hybrid phasing matrices.
A further object of the present invention is to provide a phased antenna array system having the capability of generating multiple independent transmit beams by digital beamforming techniques.